June 2014

This month's technical report showcases two new zoom lenses, the EF-S10-18mm f/4.5-5.6 IS STM (Photo 1) and the EF16-35mm f/4L IS USM (Photo 2).

The two lenses this month are categorized as ultra-wide-angle zoom lenses, and as such they can capture wider fields of range than standard zoom lenses and wide-angle lenses. They are suitable not only for landscape photos but also for snapshots of subjects at short distances in cramped rooms and for commemorative photos of large groups. These lenses are also capable of dynamic creative expressions emphasizing the perspective [*1] of outdoor objects with depth and height. And by getting extremely close to the subject, photographers can obtain radically different creative looks from subjects (distorted effects).

*1. With this effect, close objects appear larger and closer than normal and distant objects appear smaller and farther away than normal.

(1) EF-S10-18mm f/4.5-5.6 IS STM

Development objectives

An ultra-wide-angle zoom lens with a 35mm-equivalent focal length of 16 to 29 mm, this lens was developed to be lightweight and compact and is equipped with a STM [*2] to support movie recording. It is the first EF-S ultra-wide-angle zoom lens with an image-stabilizer mechanism.

• First EF-S ultra-wide-angle zoom lens with an image-stabilizer mechanism

• Movie Servo AF that operates smoothly and quietly while recording movies due to a focusing mechanism that uses a stepping motor and a lead screw in addition to a compact, lightweight rear-focusing lens element

• Image stabilizer provides a stabilization gain equivalent to about four f-stops in shutter speed [*3]

• Minimum focusing distance of 0.22 m at all zoom positions

• Circular aperture for beautiful bokeh soft-focus effects

• Full-time manual focus mechanism (when One-Shot AF is used)

*3. According to CIPA standards. Measured at a focal length of 18 mm (35mm-equivalent 29 mm) using an EOS 7D.

The following sections describe some of the lens's technical features.

The lens's optical system was newly developed to support movie recording functions while having the characteristics of an ultra-wide-angle zoom lens. The lens construction consists of 14 elements in 11 groups with a four-group zoom arrangement (Figure 1).

Aspherical lens elements are used for the large-diameter second element and the very last element to correct various aberrations, shorten the overall length, and achieve high image quality. The UD lens element (the 11th element) works to correct chromatic aberrations, resulting in excellent image quality at all zoom positions (Figure 2).

The lens adopts a rear-focusing configuration in order to support movie recording functions. Because in this configuration only the single element of the third lens group moves during focusing, Movie Servo AF can operate smoothly and quietly while recording movies.

Similarly, the image stabilization optics consist of only a single moving element in the second lens group, which permits the drive and focusing actuators to be made more compact. This plays a major part in reducing the lens's size and weight.

The lens's overall length is shortest at a focal length of about 15 mm and longest at the wide-angle end. With a minimum focusing distance of 0.22 m, the lens can focus on subjects as close as about 10 centimeters from the end of the lens.

The lens coating has been optimized with the latest simulation technologies and greatly reduces flaring and ghosting as well as provides an excellent color balance.

Feature 2 - Image stabilizer

The biggest functional feature on the lens is its image stabilizer, a first for an EF-S wide-angle zoom lens. As explained above, the image stabilizer uses an optical shift mechanism that drives one element in the second lens group perpendicular to the optical axis. Among EF-S lenses to date equipped with image stabilizers, the shortest focal length was 15 mm (35mm-equivalent focal length of 24 mm). This lens offers image-stabilized shooting at even shorter focal lengths.

And with a controller optimized to match the characteristics of the image-stabilizer unit, the image stabilizer delivers a large stabilization gain equivalent to about four f-stops in shutter speed [*3] that is effective at shutter speeds as slow as about 0.5 seconds. This allows photographers to hand-hold shots at slow shutter speeds. The camera can also distinguish between normal shooting and pan shots from a vibration-gyro signal, and thereby automatically select the best image-stabilization mode for each shot.

Feature 3 - STM and a compact, lightweight form factor

The lens has the same focusing mechanism, which uses a stepping motor and a lead screw, as that on the EF-S18-55mm f/3.5-5.6 IS STM, a standard zoom lens.[*4] Because of this focusing mechanism, the lens delivers fast, quiet autofocusing for viewfinder shooting as well as smooth, quiet Movie Servo AF when recording movies.

The lens has a maximum external diameter of 74.6 mm, an overall length of 72 mm, and a weight of about 240 grams, making it a compact, lightweight lens with all the advantages of an EF-S lens and the characteristics of an ultra-wide-angle lens (Table 1).

*4. See the August 2012 edition of the Technical Report for more details.

(2) EF16-35mm f/4L IS USM

Development objectives

This lens was developed as the first ultra-wide-angle zoom lens with an image-stabilization mechanism [*5] that pushes the boundaries of photography and creative expressions. It brings higher performance to the ultra-wide-angle lens domain while enriching Canon's f/4L lens series lineup.

*5. Among EF ultra-wide-angle full-frame zoom lenses.

The lens's main features are as follows.

• Ultra-wide-angle zoom lens with the excellent image quality of an f/4L series lens

• Provides excellent image quality at all zoom positions and in all areas of the frame thanks to aspherical lens elements and UD lens elements

• First ultra-wide-angle full-frame zoom lens with an image-stabilizer mechanism

• Image stabilizer provides a stabilization gain equivalent to about four f-stops in shutter speed [*6]

• Minimum focusing distance of 0.28 m at all zoom positions

• Robust durability for the digital age

• Circular aperture for beautiful bokeh soft-focus effects

• Excellent dust and water resistance for shooting in harsh conditions [*7]

• Silent, high-speed AF thanks to inner focusing + a ring USM

• Full-time manual focus mechanism (when One-Shot AF is used)

• Front and rear lens surfaces coated with a fluorine coating

*6. According to CIPA standards. Measured at a focal length of 35 mm using an EOS-1D X.*7. The Canon PROTECT filter, sold separately, must be attached.

The following sections describe some of the lens's technical features.

Feature 1 - Excellent image quality at all zoom positions and in all areas of the frame

Figure 3: Cross-section view of the EF16-35mm f/4L IS USM optics

The zoom lens's optical system has a newly developed four-group zoom arrangement and uses an inner-focusing configuration with the focusing lens group positioned just in front of the aperture in the second lens group. The lens construction consists of 16 elements in 12 groups (Figure 3).

The first lens group has two aspherical elements, including the front, large-diameter aspherical element. Another aspherical element is located as the last element in the fourth lens group. The inclusion of these elements dramatically reduces lens distortion, field curvature, and astigmatisms and achieves better image quality, particularly at the edges of the frame.

The fourth lens group also uses two UD elements, which minimize the occurrence of chromatic aberration of magnification at the edges, as well as in the middle of the frame, when at the wide-angle end. This allows the lens to deliver high-resolution, high-contrast image quality with little color bleeding at the edges of subjects (Figure 4).

The lens coating has been optimized with the latest simulation technologies and greatly reduces flaring and ghosting as well as provides an excellent color balance. In addition, a fluorine coating has been applied to the very front lens element (R1 surface) and very rear lens element (R2 surface) that are exposed to open air. This coating permits any dust attached to the lens surfaces to be wiped off easily with a dry cloth.

Feature 2: Image stabilizer

The biggest functional feature on the lens is its image stabilizer, a first for an EF ultra-wide-angle full-frame zoom lens. The image stabilizer uses an optical shift mechanism that moves the third lens group.

We optimized the actuator that drives the four stabilizer lens elements and adopted an ultra-low-friction drive mechanism that moves on roller balls. And with a controller optimized to match the characteristics of the image-stabilizer unit, the image stabilizer delivers a large stabilization gain equivalent to about four f-stops in shutter speed [*6] that is effective at shutter speeds as slow as about 0.5 seconds. This allows photographers to get creative hand-held expressions at slow shutter speeds. The camera can also distinguish between normal shooting and pan shots from a vibration-gyro signal, and thereby automatically select the best image-stabilization mode for each shot.

Feature 3: Improved usability in addition to reliability and durability

The lens has a maximum external diameter of 82.6 mm, an overall length of 112.8 mm, and a weight of about 615 grams, packing higher image quality and an image stabilizer in an easy-to-use size.

The external design features a much slimmer zoom ring to give the lens a good proportion, much like the beauty of converging light, as well as a better feel when held and used. The focus ring and zoom ring have been designed to emphasize precision in the pursuit of operability.

The lens barrel's mechanical structure has been redesigned, matching the design of the EF24-70mm f/4L IS USM, for greater zoom durability and to provide the barrel components with better vibration and shock resistance. Dustproof and waterproof seals have been used around the mount, the switch panel, the zoom ring, and the focus ring to prevent moisture or dust from infiltrating inside the lens so that the lens can be used in harsh conditions. Note that because the front lens section moves while zooming, Canon's PROTECT filter, sold separately, must be attached to give complete dust and water protection.

The lens comes with two accessories. The petal-shaped EW-82 lens hood attaches with a two-pronged bayonet mount and includes a lock mechanism. The hood's inner surface has been given a flocking treatment for excellent anti-reflective performance. The other accessory is the pouch-shaped LP1219 soft case.

The two zoom lenses in this month's edition allow photographers to emphasize perspective in their photos with the vast space inherent to ultra-wide-angle lenses. And by combining the lenses' image stabilization with the high sensitivity and low noise of an EOS camera, photographers can enjoy coming up with new shooting styles and creative expressions, such as shooting handheld in confined spaces with just the ambient lighting without using a tripod or flash. You are sure to find these lenses useful in creating new artworks.